<p>This study investigates the effect of heat build-up, as a function of different building modes and energy input, on the microstructure and mechanical properties of Al-Si10-Mg parts processed by Selective Laser Melting (SLM). Three different volumetric energy densities (67&#xa0;J/mm³, 70&#xa0;J/mm³ and 86&#xa0;J/mm³) were applied for building samples. The building chamber was heated at 200&#xa0;°C to reduce residual stress. The samples were processed in Horizontal (H) and Vertical (V) modes. The H and V samples were investigated using an Optical Microscope (OM), a Scanning Electron Microscope (SEM), x-ray diffraction (XRD), Vickers microhardness, and tensile tests. Moreover, the electrical conductivity (EC) of the samples was investigated<b>.</b> The amount, size, and morphology of the defects were also analyzed by Image J software. Different building modes significantly influenced the heat build-up, microstructure, and hardness at a set energy density. Vertical samples exhibited a coarser microstructure and reduced homogeneity along the growth direction (<i>z</i>-axis) compared to horizontal samples. V samples also showed significant variations in microstructure and hardness along the <i>z</i>-axis, whereas H samples maintained greater uniformity. Furthermore, the percentage of defects increased in V samples and decreased in H samples with increasing heat input. Finally, after tensile test, a misalignment in mechanical response for H and V modes has been observed at all the energy densities except the lowest one.</p> Graphical Abstract <p></p>